This invention relates in general to voltage regulators in integrated circuit (IC) technology and, in particular, to an IC regulator which is highly advantageous in supplying a constant current source to a current mode logic device used in high speed digital logic systems.
IC voltage regulators capable of providing a zero temperature coefficient regulated output voltage have already been developed. Such regulators have also been developed to supply a constant output voltage for logic circuits within a limited range of variations in the supply voltage. One manner of providing the constant output voltage in such regulators is to use a PNP transistor to provide the constant current in the shunt feedback transistor of the regulator. However, the disadvantage in such a system is the dependency on the absolute characteristics of the PNP transistor, which limited the voltage supply variation range because of the current limitations on the vertical PNP. In addition, the excess phase shift induced by the slow response of the PNP transistor imposed the use of a large rolloff capacitor in the regulator which became impractical in IC circuit applications and sometimes made the regulator oscillation prone.
It is therefore an object of this invention to provide an IC regulator which is fully temperature and supply voltage compensated so as to be useful in high speed digital logic, namely, a current mode logic environment.
Another object of this invention is to provide an IC regulator which is fully temperature and supply voltage compensated so as to be responsive to a wide range of variations in supply voltage and to eliminate any excess phase shift thus making the regulator less prone to oscillation.